Instrumental Analysis Exam 4: GC and LC questions
with verified answers
3 types of stationary phase in GC Ans✓✓✓ ∙solid adsorbants
∙liquids coated on solid support
∙bonded-phase supports
Bonded-phase GC (Cross-linked phases) Ans✓✓✓ -covalently attach
stationary phase to the solid support material
- avoids column bleeding in GLC
- bonded phases are prepared by reacting the desired phase with a
silica-surface
-reactions form an Si-O-Si bond between the stationary phase and
support
-reactions form an Si-C-C-Si bond between the stationary phase and
support
Characteristics of common liquid stationary phases for GLC Ans✓✓✓
Components of a simple GC system Ans✓✓✓ 1. Gas source for mobile
phase (with pressure and flow regulators)
2. Injector or sample application system (sample inlet)
3. Chromatographic column (with oven for temperature control)
4. Detector & computer or recorder
, Conc.-sens vs Mass-sens detector Ans✓✓✓ Concentration-sensitive
detector responds to the
concentration of the *analyte in the mobile phase* (the mobile phase is
directly involved in the
signal formation). (e.g. TCD and ECD)
Mass-sensitive detector responds to the number of molecules or ions
that *contact with the detector* (the mobile phase is not directly
involved in the signal formation). (e.g. FID, AED, and FPD)
ECD advantages Ans✓✓✓ Useful for environmental testing:
-detection of chlorinated pesticides or herbicides
-detection of polynuclear aromatic carcinogens
-detection of organometallic compounds
- selective for halogen- (I, Br, Cl, F), nitro-, and sulfur-containing
compounds
- detects polynuclear aromatic compounds, anhydrides and conjugated
carbonyl compounds
Electron capture detector Ans✓✓✓ radioactive decay-based
selects compounds with EN atoms like halogens-
Based on the capture of electrons by electronegative atoms in a
molecule
with verified answers
3 types of stationary phase in GC Ans✓✓✓ ∙solid adsorbants
∙liquids coated on solid support
∙bonded-phase supports
Bonded-phase GC (Cross-linked phases) Ans✓✓✓ -covalently attach
stationary phase to the solid support material
- avoids column bleeding in GLC
- bonded phases are prepared by reacting the desired phase with a
silica-surface
-reactions form an Si-O-Si bond between the stationary phase and
support
-reactions form an Si-C-C-Si bond between the stationary phase and
support
Characteristics of common liquid stationary phases for GLC Ans✓✓✓
Components of a simple GC system Ans✓✓✓ 1. Gas source for mobile
phase (with pressure and flow regulators)
2. Injector or sample application system (sample inlet)
3. Chromatographic column (with oven for temperature control)
4. Detector & computer or recorder
, Conc.-sens vs Mass-sens detector Ans✓✓✓ Concentration-sensitive
detector responds to the
concentration of the *analyte in the mobile phase* (the mobile phase is
directly involved in the
signal formation). (e.g. TCD and ECD)
Mass-sensitive detector responds to the number of molecules or ions
that *contact with the detector* (the mobile phase is not directly
involved in the signal formation). (e.g. FID, AED, and FPD)
ECD advantages Ans✓✓✓ Useful for environmental testing:
-detection of chlorinated pesticides or herbicides
-detection of polynuclear aromatic carcinogens
-detection of organometallic compounds
- selective for halogen- (I, Br, Cl, F), nitro-, and sulfur-containing
compounds
- detects polynuclear aromatic compounds, anhydrides and conjugated
carbonyl compounds
Electron capture detector Ans✓✓✓ radioactive decay-based
selects compounds with EN atoms like halogens-
Based on the capture of electrons by electronegative atoms in a
molecule
